Optimization of conductivity and transparency in amorphous In-ZN-O transparent conductors

Amorphous mixed metal oxide TCOs are of increasing interest due to the excellent opto-electronic properties and smoothness (RRMS ≪ 0.5 nm) obtained for sputtered films deposited at less than 100 °C. In particular, for amorphous In-Zn-O (a-IZO) films grown from a ceramic target with 10 wt. % ZnO in In2O3, the current industry standard, conductivities σ ≥ 2500 S/cm are common. Here, we have investigated the combined materials phase space of oxygen stoichiometry and metals composition (In:Zn ratio) and made two key discoveries. First, that high conductivity a-IZO thin films can be made with substantially less indium provided that a corresponding change is also made in the oxygen content. And second, that for all compositions of a-IZO, the electron mobility (μ) and carrier concentration (N) fall on a single common curve when plotted as μ vs N.